The present invention relates to an ink jet color filter resin composition for the production of a color filter for use in color liquid crystal displays, color image pick-up elements and the like by an ink jet system, a color filter having a pixel pattern formed from the color filter resin composition by an ink jet system and a process for producing a color filter from the color filter resin composition by an ink jet system.
A color filter for use in color liquid crystal displays (LCD) and the like is incorporated in a color liquid crystal display or the like and serves to improve picture quality and provide a primary color to each pixel.
Known processes for producing such a color filter include one in which a coating film of a radiation sensitive resin is exposed to radiation through a photomask to cure exposed portions, the exposed portions are developed to remove radiation unexposed portions of the coating film so as to form a pattern and the pattern is dyed (dyeing process) and a photography process in which a composition comprising a red, green or blue colorant dispersed in a radiation sensitive resin is used to form a coating film, and the coating film is exposed to radiation and developed as described above. However, these processes involve such problems that the pixel pattern forming step is complicated and the cost is high.
JP-A 59-75205, JP-A 61-245106 and JP-A 63-235901 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) disclose processes for producing a color filter by an ink jet system comprising the step of forming the pigmented layer of a color filter with an ink jet head. In these processes, the control of a position for discharging droplets of a color filter resin composition is easy and a waste of the resin composition is small, thereby making it possible to reduce production cost.
However, the above conventional processes for producing a color filter by an ink jet system may have such a problem that the color density of a color filter resin composition discharged becomes nonuniform. Therefore, JP-A 4-261503 and JP-A 7-318723 propose methods for suppressing nonuniformity in the color density of a pixel pattern by controlling the discharge of a color filter composition.
In these publications, thorough studies are not made on the composition suitable for an ink jet system of a color filter resin composition and details of a color filter production process are not fully disclosed.
The inventors of the present invention have studied in detail the behavior in the color filter production process of a color filter resin composition used for the production of a color filter by an ink jet system and have found it necessary to reduce the drying speed of liquid drops of the color filter resin composition when it is discharged, suppress an excessive rise in the viscosity of liquid drops by drying and prevent the deposition of a solid content in order to discharge liquid drops of the color filter resin composition linearly by preventing a used ink jet head from being clogged because the area of each pixel pattern forming a color filter is very small.
The present invention has been made based on the above finding in view of the above situation of the prior art.
It is therefore an object of the present invention to provide a color filter resin composition which can simplify the step of forming a pixel pattern and is optimized for the production of an inexpensive color filter by an ink jet system.
It is another object of the present invention to provide a color filter having a pixel pattern formed from the above color filter resin composition by an ink jet system.
It is a further object of the present invention to provide a process for producing a color filter from the color filter resin composition by an ink jet system.
Other objects and advantages of the present invention will become apparent from the following description.
According to the present invention, firstly, the above objects and advantages of the present invention are attained by an ink jet color filter resin composition (to be referred to as xe2x80x9cfirst composition of the present inventionxe2x80x9d hereinafter) which comprises (A) a colorant, (B) a binder resin and (C) a solvent having a boiling point of 245xc2x0 C. or more at normal pressure.
According to the present invention, secondly, the above objects and advantages of the present invention are attained by an ink jet color filter resin composition (to be referred to as xe2x80x9csecond composition of the present inventionxe2x80x9d hereinafter) which comprises (A) a colorant, (B) a binder resin and (C) a solvent having a boiling point of 245xc2x0 C. or more at normal pressure and which has a contact angle between it and a pixel bank formed from a resin composition for forming a color filter bank of 40xc2x0 or more.
According to the present invention, thirdly, the above objects and advantages of the present invention are attained by color filter having a pixel pattern formed by an ink jet system from an ink jet color filter resin composition which comprises (A) a colorant, (B) a binder resin and (C) a solvent having a boiling point of 245xc2x0 C. or more at normal pressure or an ink jet color filter resin composition which comprises the above components (A), (B) and (C) and has a contact angle between it and a bank formed from a resin composition for forming a bank of 40xc2x0 or more.
According to the present invention, fourthly, the above objects and advantages of the present invention are attained by a process for producing a color filter from the above resin composition of the present invention by an ink jet system, comprising:
the step of discharging the above resin composition from an ink jet head into light transmitting regions on the surface of a transparent substrate having banks formed thereon to store the resin composition in the light transmitting regions defined by the banks;
the step of forming a pixel pattern by drying the resin composition stored in the light transmitting regions; and
the step of forming a protective layer to cover the pixel pattern.